Photographic emulsions



' 4o acetate, and Lederer British Patent No. 26,503 7, 1933, and No. 1,954,336, granted April 10, 1934.

'Patented Mar. 8,1938 Q I I I I I UNITED STATES PATENT orFl-ce PHOTOGRAPHIO EMULsIoNs Martti Salo, Rochester, N. Y.,- assignor, by mesne assignments, to Eastman Kodak Company, Jersey City, N. J., a corporation of New Jersey No Drawing. Application April 16, 1936,

semi No.74,815 I 15 Claims; (C1. 95-7) This invention relates to photographic emulmono-basic simple and mixed cellulose esters sions and particularly to emulsions in which a may be hydrolyzed and that as the degree of hydrolyzed cellulose ester is used as the protechydrolysis increases. the esters become soluble v tive colloid for the light-sensitive salt.' in the more polar types of solvents such as 1,4

5 Various substances have been suggested and dioxane, beta-methoxy-ethyl alcohol and ethyl 6 tried as carriers or protective colloids for the lactate. On further hydrolysis a stage is reached light-sensitive salts used in photography, but, as where these esters become soluble in solvent mixis well-known, none has been found which pos-- tures containing as much as 50% water. sess the unique chemical and physical proper- On account of the presence of appreciable l0 ties of gelatin. Collodion was used for this puramounts of water, a solvent mixture such as 10 pose before the discovery of the useful propertiesethyl lactate and water will dissolve the hydroof gelatin as a photographic carrier and even up lyzed cellulose ester'and will also dissolve appreto the present time, it is used in certain comciable quantities of inorganic salts such as somercial processes. Two methods of processing dium chloride, sodium bromide, silvernitrate,

l5 photographic plates were developed, namely, the etc. It is therefore possible to precipitate alightdry and the wet process. According to the first sensitive halide such as silver bromide in the method, the light sensitive halides were precipicolloidal dispersion of the cellulose ester, sometated in an alcohol-ether solution of collodion what similar to the manner in whichthe silver which was then coated onto a glass or other sup: bromide is dispersed in gelatin. On coating' a I port and exposed and processed in a manner solution containing the silver halide suspended 20 similar to the present gelatin procedure. The in the hydrolyzed cellulose ester onto a suitable second process involves treating an iodized 001- support, there is obtained a light-sensitive coatlodicn plate in a silver nitrate bath immediately ing which may be used to record photographic prior to exposure and development. images.

Of these two early processes employing collo- The cellulose esterswhich may be used as prodion, only the wet plate process has continued tective colloids for. the light-sensitive salts acto be of any importance. One objection to the cording to my invention, include the monoccllodion process is the low water permeability basic simple and mixed acid esters of cellulose of cellulose nitrate films. Coincident with this such as cellulose acetate, cellulose acetate proan is the insolubility of cellulose nitrate in solvent pionate, cellulose acetate butyrate and others. 0

r mixtures containing appreciable amounts ofwa- These are hydrolyzed to an acyl content of about ter, which consequently prevents the use of 19 to about 33%. Hydrolyzed esters having an water-soluble salts such as the common alkali acyl content of 19 to 26% are particularly usehalides used in forming the light-sensitive halful, due to their high water permeability. The

3.1 ides of the present gelatin process. hydrolyzed esters used according to my inven- 35 I The use of cellulose acetate as a carrier for tion have been prepared prior to the present inlight-sensitive salts, has also been suggested. vention. Esters hydrolyzed to an acyl content Eichengrun U. S. Patent No. 752,388, February of about 30% are described in Staud and Web- 16, 1904, suggested alcohol solutions of cellulose ber U: S. Patents No. 1,896,145, granted February of 1906' suggested cellulose acetates soluble in Cellulose esters hydrolyzed to an acyl content acetic acid as carriers of light-sensitive salts. of below 30% are described in the co-pending 'Up to the present time, however, photographic application of Charles R. Fordyce Serial No.-

emulsions formed in this way have not been 62,333, filed February 4, 1936. successful and have not gone into general use. As stated above, the solubility of the cellulose 45 The principal object of the present invention esters in various solvents changes as the "degree is to provide a carrier or protective colloid for of hydrolysis is increased. In order to form a light-sensitive silver salts which has the physidispersion of light-sensitive inorganic salts in cal and photographic properties of gelatin. the hydrolyzed cellulose ester solution, it is nec- This object is accomplished according to the essary to use a solvent-water mixture which dis-. 50

present invention by dispersing silver halides in solves both the cellulose ester and the inorganic the presence of a-water-susceptible, hydrolyzed, salts used to precipitate the-light-sensitive 'salt. mono-basic, simple or mixed acid ester of cellu- On the basis of hydrolyzed cellulose acetate as a lose. A criterion, the following solvent-water mixtures -It is known that cellulose acetate and other have been found suitable: 55

Percent by weight water in mixture Acetone water-.. 5-40 1,4-dioxane water 0-50 Methyl-cellosolve water 0-25 Ethyl lactate water L 0-50 Hydrolyzed cellulose acetate of 19 to 26% acetyl is soluble as follows:

- Percent by ,weight water in mixture Acetone water 35-80 Ethyl lactate water 35-70 Methyl cellosolve water -65 1.4 dioxane water, -65 Ethyl alcohol water -70 n-propyl alcohol water -80 The following examples illustrate methods of forming a light-sensitive coating according to my invention:

Example! A-solution of 1.9 grams of potassium bromide in 5 cc. ofa 1:1 ethyllactate-water mixture was mixed with a solution containing 3 grams-of cellulose acetate hydrolyzed to an acetyl content of about 33% dissolved in 21 grams of a solvent mixture containing 75% ethyl lactate and 25% water. To this was then added slowly with good stirring, a solution of 2.9 grams of silver nitrate dissolved in 5 cc. of a 1:1 solution of ethyl lactate and water. Finely divided silver bromide was thereby produced in suspension in the solution.

After diluting with 20' cc. of 1:1 ethyl lactate-. water,,the emulsion was poured slowly into 200 to 300 cc. of water causing the acetateand the occluded salts to be precipitated. The precipitated material was thoroughly washed with water and then dried in an air drier, following which the dried material was dissolved in a solvent consisting of 54.5% ethylene chloride, 27.2 methyl alcohol and 18.8% beta-methoxy-ethyl alcohol, one part of the dried material being dissolved in 10 parts of the solvent mixture. This solution was then coated onto a glassplate in a uniform coating of approximately --.001" thick.

mersed in a developing bath of the following composition: 7

-Water 00' 500 Monomethyl p-aminophenol' sul- I 1 grams 3.1 Sodium sulphite do 4 5.0 Hydroquinone do 12.0 Sodium carbonate do 67.5 Potassium bromide do. 1.9

Water to make; liter 1 Example 11 A solution of 6.6 grams of. potassium bromide dissolved n 32 grams of a l :1 ethyl lactate-water mixture was mixed with a solution containing 9 grams of-cellulose acetate butyrate hydrolysed to an acetyl content of 27% and butyryl content of 4.5% in 111 gramsof a solvent mixture composed of an ethyl lactate-water mixture in the propor-,

- ing the following composition:

This emulsion was coated onto baryta coated paper in an even coating of approximately .001" thick and exposed in a contact printer using average negatives. The paper carrying the emulsion was then placed in a developing solution hav- Water c 500 v Monomethyl p-aminophenol sul- I fate grams 3.1 Sodium sulflte do 45.0 Hydroquinone do 12.2 Sodium carbonate do 67.5 Potassium bromide do 1.9 Water to make liter 1 The penetration of the developer was found I be slow, but when the developer was diluted 1:1

with water, the penetration was much more rapid. The addition of ethyl carbamate to the developer in the amount of 20 grams of ethyl carbamate to cc. of developer and 100 cc. of water was found to further increase the rate of penetration of developer. The prints were fixed for ten minutes in a bath containing 10 grams of sodium thlosulfate and 5 grams of potassium thiocyanate dissolved in 50 cc. of water. It was found that the potassium thiocyanate, in addition to being a sol-' -vent for the silver halide, served as a swelling agent forthe hydrolyzed esters and thereby. accelerated the fixing process.

Example In A solution of 4.2 grams of potassium bromide in a mixture of 5 cc. of beta-methoxyethyl alco- 1101 and 9 cc. of waterwas added to a solution containing 6 grams of cellulose acetate hydrolyzed to'an acetyl content of about 24.4% in 21.6 cc. of

betafme thoxymethyl alcohol and 14.4 cc. of water. 5.4 grams of silver nitrate dissolved in 9 cc. of water and 5 cc. of beta-methoxyethyl alcohol 'were then added with good stirring and silver Example 11 wasdiluted with 4 parts of water.

Emulsions formed from hydrolyzed cellulose esters, asdescribed above have numerous advantages' over ordinary gelatin emulsions. They have good mechanical strength and are not so liable to breaking and rupturing in processing.

. Theyare insoluble in water and thereby permit higher temperature baths to be'used in processing, as'is frequentlyv required in tropical photographic :work. Emulsions formed in this way also have the advantage that greater uniformity may be obtained in their manufacture.

The compounds and methods of procedure the process of my invention due to their favorable water susceptibility, emulsions may be made with cellulose. esters having a greater acyl content even. though the water susceptibility of these Y emulsions is less favorable. A lower limit of 19% has been placed on the acyl value of the hydrolyzed esters. This is an approximate value, since esters of slightly lower acyl content may be used 5 in applications where "the water solubility is not a hindrance. Because of this water solubility. v

' however, cellulose acetates of less than 19% acetyl would not ilnd wide practical application. It is onlyby thescope of the appendedclaims.

a.-. scribed above maybe varied within wide limits. Although I have found that the cellulose esters "containing 19 to 24% acyl are most suitable for :to'be understood that my invention is limited u I claim: 1. The method of making a sensitive photo graphic emulsion which comprises dispersing a silver halide in a solution of a hydrolyzed cellufiloseorganic acid ester of approximately 19% to approximately 33% acyl. content. v

2.. Themethod of making a sensitive photographic emulsion which comprises dispersing a silver-halide ing -a solution of a hydrolyzed celluj lose mixed organic acid ester of approximately 19% to approximately 33% acyl content.

3.1 The method of making a sensitive photo- I graphic emulsion which' comprises dispersing a silver halide in a solution of hydrolyzed cellulose 15 acetate butyrate of approximately 19% to approximately 33% acyl content.

4. The method of making a sensitive photographic emulsion which comprises dispersing a silver halide in a solution of hydrolyzed cellulose acetate or approximately -19% to approximately acetylcontent. A

5. A sensitive photographic emulsion comprising a silver halide dispersed in ahydrolyzed cellulose organic acid ester of approximately 19% to approximately 33% acyl content.

6-. A sensitive photographic emulsion comprising a silver halide dispersed in a hydrolyzed cel- V i lulose mixed organic acid ester of approximately 19% to approximately 33% acyl content.

'7. A sensitive photographic emulsion comprising a. silver halide dispersed in hydrolyzed cellulose acetate butyrate of approximately 19% to approximately 33% acyl content.

8. A sensitive photographic emulsion compris-' ing a silver halide dispersed in hydrolyzed cellulose acetate 01 approximately 19% to approximately 33% acetyl content.

9. The method of making a sensitive. photographic emulsion which comprises dissolving a hydrolyzed cellulose organicacid ester of approximately19% to approximately 33% acyl content in a solvent mixture containing approximately 50% water, dispersing a silver halide in the solution, and curing the resulting dispersion.

10. The method of making a sensitive photographic emulsion which comprises dissclving a hydrolyzed cellulose organic acid ester of ap-'- v proximately 19% to approximately 33% acyl content in a solvent mixture containing approximately 50% water, dispersing a silver halide in the U solution, washing the excess salts from the dispersion with water, redissolving the cellulosic material containingthe silver halide in a solvent- 1 water mixture, and curing the resulting dispersion.

11. A sensitive photographic emulsion comprising a silver 'halide dispersed in hydrolyzed cellulose acetate having an acetyl content of 19% to 26%.

12. The method of making a sensitive photographic emulsion which comprises dispersing a. silver halide in hydrolyzed cellulose acetate having an acetyl content of 19% to 26%.

13. The method ofmaking a sensitive photographic emulsion which comprises dissolving hymately equal proportions, dispersing 'a silver halide in the solution,

and curing the resulting dispersion.

mam SALO. 

